Extensible coupling for well pipes



April 7, 1970 c, c. BROWN ET AL 3,504,936

EXTENSIBLE COUPLING FOR WELL PIPES 3 Sheets-Sheet 1 Filed Oct. 12, 196? lA/VE/VTORS.

CIC'fRO 6. BROWN JAMES .D. MOTT ATTORNEY April 7, 1970 c. c. BROWN- ET AL 3,504,936

EXTENSIBLE COUPLING FOR WELL PIPES 3 Sheets-Sheet 2 Filed Oct. 12, 1967 INVENTOAS. C'IJERO 6'. BROWN JAMES .D M077 A TTORNEY April 7, 1970 Filed Oct. 12, 1967 c. c. BROW 'ET AL EXTENSIBLE COUPLING FOR WELL PIPES 3 Sheets-Sheet 5 9 4" Jam d/'ERO d. BRO WN JAMES D. MOTT INVENTORS'.

rromvsy United States Patent Office 3,504,936 EXTENSIBLE COUPLING FOR WELL PIPES Cicero C. Brown and James D. Mott, Houston, Tex.; said Mott assignor to Brown Equipment & Service Tools, Inc., Houston, Tex., a corporation of Texas Continuation-impart of application Ser. No. 618,464, Feb. 24, 1967. This application Oct. 12, 1967, Ser. No. 674,983 Int. Cl. F16] 17/02, 27/12, 33/18, /00, 27/12 U.S. Cl. 285106 4 Claims ABSTRACT OF THE DISCLOSURE An extensible coupling for use in well pipe strings, particularly rotary drill strings, to permit relative longitudinal movement between sections of the pipe string to accommodate longitudinal movements of the upper end of the pipe string while maintaining the lower end relatively stationary longitudinally. Telescoping male and female tubular members having elongated spline elements are connected for longitudinal, relative nonrotative movement. Anti-friction bearings are arranged between the members to provide relatively friction-free movement. A plurality of sealing elements are disposed between the members to assure maximum sealing efliciency.

OTHER APPLICATIONS This application is a continuation-in-part of the copending application of Cicero C. Brown, Ser. No. 618,464, filed Feb. 24,1967, now abandoned.

BACKGROUND OF THE INVENTION In drilling wells by the conventional rotary method, particularly from a floating drilling platform, the platform will be subjected to vertical movements in response to the passage of waves .over the surface of the water body on which it is afloat. This necessarily produces a corresponding up and down movement of the drill pipe string, which is a serious hindrance to the drilling operation, particularly to maintenance of a constant weight on the drill bit during the drilling operation, since upward movement tends to pull the bit and drill collars off bottom while downward movement may tend to apply undue downward pressure on the drill string and the bit.

Various types of extensible couplings, commonly called slack joints, have heretofore been employed to overcome this difficulty by providing an extensible coupling in the drill pipe string which will allow for the vertical movements of the floating platform while maintaining the bit in constant contact with the bottom of the well and at the same time maintaining rotation of the drill string necessary to turn the drill bit. Such conventional joints employ various forms of splined connections between telescoping members of the coupling to accommodate the longitudinal movement which occurs. However, such conventional couplings are subject to very severe wear and to unbalance pressure forces such that they must be replaced frequently and may, in some instances, become broken by reason of the extensive wear thereon. Moreover, many of the conventional couplings are made relatively complex in an effort to meet the conditions encountered and their complicated construction necessarily creates problems in maintaining the parts in efficient working condition under the severe loads frequently imposed thereon.

Furthermore, under the severe operating conditions commonly encountered conventional couplings are subject to leakage between the coupling members which may permit circulating drilling fluid to by-pass the drill bit, with a consequent loss of drilling efliciency.

3,504,936 Patented Apr. 7, 1970 SUMMARY OF THE INVENTION The present invention contemplates a structure employing telescoping male and female members connected for longitudinal, relative nonrotative movement comprising, elongate splines on one member received in spline grooves on the other member and having anti-friction bearings arranged therebetween to provide relatively friction-free movement between the members, and a sealing unit disposed between the members arranged to provide a high degree of efficient sealing between the members while permitting the required relative longitudinal movement therebetween.

It is a primary object of the present invention to provide an improved and greatly simplified form of extensible coupling as compared with more conventional couplings.

An important object is the provision of a coupling in which the spline members are provided with a novel form of antifriction bearing between the spline elements.

A further object is to provide an extensible coupling which includes a sealing assembly comprising a plurality of seal elements disposed between the coupling members to assure maximum sealing efficiency under severe operating conditions.

A more specific object is to provide an extensible coupling in which the sealing unit or assembly between the coupling members comprises upper and lower sleeve-type seals responsive to increasing pressure from one direction to increase their Sealing efficiency, the lower one of the sealing elements being greater in length than the upper one to provide a greater sealing area than the upper sealing element, and a third sealing element between the upper and lower sealing elements arranged to block fluid leakage between the coupling members in a direction opposite the said one direction.

Since couplings of the kind here contemplated are made part of a rotating string of pipe, the coupling members will ordinarily be subjected to some torsional forces which, in some instances, may be sufficiently great to impose severe frictional forces likely to cause substantial and even destructive wear on the relatively movable coupling elements.

To meet the various conditions likely to be encountered the present invention contemplates two different forms of antifriction bearings between the coupling elements. In one form the bearings are roller-type hearings in the form of short cylinders. In the other modification, especially useful where severe torsional forces are anticipated, the bearings are in the form of more conventional balls which can accommodate themselves more effectively, without binding or excessive friction generation, between bearing races which tend normally to twist in response to high torsional forces acting on the couplings.

Other and more specific objects and advantages of this invention will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawing which illustrates a useful embodiment in accordance with this invention.

In the drawing:

FIG. 1 is a longitudinal quarter-sectional view of the exemplary coupling with the coupling members in their relatively contracted positions;

FIGS. 2 and 3 are cross-sectional views taken along lines 2-2 and 3-3, respectively, of FIG. 1;

FIG. 4 is a fragmentary sectional view, on an enlarged scale, taken along line 44 of FIG. 2;

FIG. 5 is an exploded perspective view, partly in section, of the sealing assembly employed in the coupling;

FIG. 6 is a view similar to FIG. 1 illustrating a modified form of the present invention;

FIG. 7 is a cross-sectional view taken along lines 7-7 of FIG. 6; and

FIG. 8 is a fragmentary view similar to FIG. 4 but taken on line 8-8 of FIG. 7.

Referring to the drawing, the coupling comprises a tubular male member, designated generally by the numeral 10, and a tubular female member, designated generally by the numeral 11, adapted to telescopically receive the male member for relative longitudinal movement. The coupling will ordinarily be disposed in vertical position with the male member uppermost, although the positions of the members may be reversed.

The male member 10 is composed of an upper section 12 and a lower section 13 of smaller external diameter than upper section 12, the two sections being interconnected by means of a reducer coupling 14 threadedly connecting the adjacent ends of the sections comprising the male member. The upper end of upper section 12 is enlarged to define the internally threaded box or socket 15 by means of which the male member is connected to an adjacent section of a pipe string P. The exterior of upper section 12 of the male member is reduced in diameter beginning at a point spaced just below socket 15 to form the downwardly facing shoulder 16 and to accommodate the Wall thickness of female member 11 to provide an externally flush surface for the coupling throughout its length.

Female member 11 is likewise made up of an upper section 17 and a lower section 18 threadedly connected to upper section 17 by means of a threaded flush joint 19. The lower end of lower section 18 is internally threaded to threadedly receive the upper end of an adapter collar 20 by which female member 11 is connected to a sub-adjacent section of pipe P (not shown). The inner end of adapter 20 forms an upwardly facing annular shoulder 21 in the lower end of the bore of section 18, for purposes to be described hereinafter. Upper section 17 is provided on its inner wall surface with at least two angularly spaced, inwardly projecting elongate male splines 22 having parallel side edges 2323. These splines are formed on separate segments 17a which are subsequently welded in place as permanent parts of section 17 during assembly of the structure. The male splines project into longitudinal spline slots 24 provided in the outer surface of upper section 12 of the male member. Spline slots 24 are defined by parallel side walls 24a and upper and lower end walls 241) and 240, respectively. The lengths of slots 24 are sufficiently greater than the lengths of splines 22 to permit the desired extent of relative longitudinal movement between the coupling members. The upper end of section 17 extends a short distance above the upper ends of splines 22 and is adapted to abut shoulder 16 to limit the relative contractive movement between the coupling members. Elongation of the coupling will be limited by engagement of the lower end of spline 22 with lower end wall 24a of the spline slots 24. A bronze wear ring 25 is arranged in the inner periphery of the upper end of section 17 to provide a close fitting bearing surface about the exterior of section 12 of the male member.

A novel form of antifriction bearing is provided between splines 22 and the walls of spline slots 24. The Width of slots 24 is made substantially greater than the width of spline 22 to provide a bearing race 26 there between which include convexly curved upper and lower slot portions 27 and 28, respectively, provided in the body of each spline adjacent its opposite ends, as best seen in FIG. 4.

Bearing race 26 is fillled with a plurality of parallel roller bearings 29, each in the form of a short cylinder having flat ends adapted to fit snugly between the walls defining the bearing race between the splines and the spline slots. The bearings 29 are loose from each other, that is, they are not mounted in a clip or mounting ring, and are thus free to roll around the surfaces defining the bearing race to accommodate themselves both to relative longitudinal movements between the coupling members and also to relative lateral shifting movements between the coupling members, and thus effectively reduce friction and prevent any binding between the coupling members during relative extension and retraction thereof.

A seal assembly, designated generally by the numeral 30, is mounted in a portion of the annular space 31 defined between male section 13 and female section 18 below the spline connection. Assembly 30 is held against longitudinal movement between shoulder 21 and an internal shoulder 32 provided on the inner wall of section 18'. One or more ports 33 extend through the wall of section 18 at a point just above the upper end of seal assembly 30 to provide fluid pressure communication between annular space 31 and the exterior of the coupling and serve primarily as pressure equalizing ports.

Seal assembly 30 is made up of a plurality of vertically spaced-apart annular seal elements which, starting from the lower end of the assembly, include a lower primary seal element 34, which is preferably of the sleeve-type, an intermediate blocking seal element 35, preferably of the lip or cup-type, and an upper back-up seal element 36, of a downwardly tapering, generally conical configuration. Each of the seal elements is constructed of any suitable and known flexible, resilient composition.

Primary seal element 34 has its upper end secured, as by conventional molding or vulcanizing procedures, to a metal mounting ring 37, preferably constructed of bronze or other metal resistant to salt water corrosion, and dimensioned to have a snug sliding fit between the opposed surfaces of sections 13 and 18 of the coupling members. The lower end of seal element 34 is molded or otherwise secured to a bronze end ring 38 having a plurality of radial passages 39 therethrough. A metal spacer sleeve 40 is arranged about the exterior of sleeve seal element 34 with its upper end in abutting relation to mounting ring 37 and its lower end encircling end ring 38 and adapted to rest on shoulder 21. A plurality of vertical channels 41 are formed inside the lower end of the bore of spacer sleeve 40 to register with passages 39 and this registering arrangement is maintained by means of a plurality of locking screws 42 connecting sleeve 40 to ring 38, as best seen in FIG. 3.

A seal 43 of the conventional O-ring type is seated in the exterior of mounting ring 37 to sealingly engage the inner wall of section 18.

It will be recognized that with the described construction and arrangement of seal element 34, it will be effective to seal against upward leakage of fluid between the coupling members which will enter the space between spacer sleeve 40 and seal element 34 and act against the exterior thereof. Thus, the greater the pressure from the interior of pipe P the tighter the seal provided by seal element 34.

Intermediate or blocking seal element 35 is seated in an annular groove 44 provided in the inner periphery of mounting ring 37 and is dimensioned to be in continuous sealing engagement about section 13 of the male coupling member. The spaced sealing lips 35a on the inner face of element 35 are arranged to seal with the bottom of groove 44 in response to fluid entering openings 44a to block fluid flow in either direction and particularly to oppose downward flow of fluid along the lower seal element and section 13, such as might enter annular space 31 through ports 33.

Upper seal element 36 is designed to function as a back-up seal for seal element 34 in that should the latter and seal element 35 fail, seal element 36 could function to prevent leakage of fluid upwardly between the coupling members. To this end, seal element 36 is preferably made of the downwardly tapering conical shape and is secured to depend from a mounting ring 36a, preferably constructed of bronze and dimensioned to have a snug sliding fit between the opposed concentric surfaces of sections 13 and 18. A seal element 45, of the conventional O-ring type, is seated in the external periphery of mounting ring 36a to sealingly engage the inner wall of section 18. A spacer sleeve 46 is positioned about the exterior of seal element 36 between mounting rings 37 and 36a to support seal element 36 in suitably spaced relation to the lower seal element. The longitudinal dimensions of the several contiguous spacers and mounting rings will be selected so that Sealing assembly 30, after insertion into annular space 31 through the lower end of section 18, may be urged into firmly held engagement with shoulder 32 by the upper end of adapter 20 when the latter is screwed into the lower end of section 18 in assembling the structure.

Sleeve element 34 will be made substantially greater in length than sleeve element 36, so that sleeve element 34 will provide a correspondingly greater area of sealing contact about section 13, as this lower seal will constitute the primary seal against upward leakage of fluid between the coupling members.

Referring to the modification illustrated in FIGS. 6 to 9, inclusive, the coupling comprises the tubular male member, designated generally by the numeral 110, and the tubular female member designated generally by the numeral 111, adapted to telescopically receive the male member for limited relative longitudinal movement.

The male member is composed of an upper section 112, an intermediate section 112a, and a lower section 113 of smaller external diameter than the upper and intermediate sections. A threaded pin-and-box connection 114a connects the upper end of section 112a to the lower end of section 112, and a reducer coupling 114 connects the lower end of section 112a to the upper end of section 113. The upper end of section 112 carries the enlarged internally threaded box 115 for connecting the male member to pipe string P.

Female member 111 is likewise made up of a plurality of coaxial interconnected sections, including an upper section 117, an intermediate section 117a and a lower section 118. A threaded pin-and-box connection 119 connects the upper end of intermediate section 117a to the lower end of upper section 117. A threaded pin-and-box connection 118a connects the lower end of section 117a to the upper end of lower section 118. The lower end of the latter is internally threaded at 118b to threadedly receive the upper end of an adapter collar 20 by which female member 111 is connected to a sub-adjacent section of pipe P (not shown). The inner end of adapter 120 forms an upwardly facing annular shoulder 121 in the lower end of the bore of section 118 and serves purposes to be described hereinafter.

The upper end of upper section 117 is counterbored to define the chamber 100 and is internally threaded at its upper end to receive the externally threaded end of an annular bushing 101 which slidably surrounds the upper end of section 112. A sealed piston 102 is slidably disposed about section 112 inside chamber 100 and is longitudinally movable therein between limiting abutments formed by the inner end of bushing 101 and the bottom of chamber 100.

Intermediate section 117a is provided on its inner wall surface with at least two angularly spaced inwardly projecting elongate male splines 122 having parallel arcuate recesses 123-123 along its side edges which are joined at their ends by convex arcuate end portions 127. These male splines are formed on separate segments 104 which are inserted through suitable openings 105 initially made through the wall of section 117a and carry at their upper ends outwardly extending arcuate flanges 106 adapted to be received in a seating recess 107 formed in the inner wall section 117 just above the upper end of section 117a. Caps 108 are subsequently welded into openings 105 to close the same after the male splines and bearing elements are in place.

The male splines project into longitudinal spline slots 124 provided in the outer surface of intermediate male 7 section 112a. Spline slots 124 are defined by parallel side walls 124a and upper and lower end walls 12% and 1240, respectively. The junctions between the side walls 124a and end walls 124b and 124c with the bottoms of slots 124 are made arcuate to define ball races 109 complementing the arcuate configuration of recesses 123. The length of slots 124 is made sufficiently greater than the length of male splines 122 to permit the desired extent of relative longitudinal movement between the coupling members, which will be limited by the abutment of end walls 124a and 12411 with the related ends of male splines 122.

The width of slots 124 is made substantially greater than the width of splines 122 to provide a space 126 which forms the bearing race therebetween, defined in part by the complementary arcuate recesses 123 and 109, and including upper and lower race portions 126a and 12611 respectively.

Bearing race 126 is filled with a plurality of bearing balls 129 arranged to be in free continuous rolling engagement with one another, whereby they can readily accommodate themselves to relative longitudinal movements between the coupling members and also to relative lateral shifting movements between the coupling members and more importantly, to any relative twisting move ments between the coupling members resulting from torsional forces therebetween. This freedom of movement will effectively reduce friction and prevent any binding between the coupling members during relative extension and retraction thereof.

In construction of the device, in order to accommodate the small helical configuration which may develop in the elongate splines under the torsional forces to which they are subjected in operation, the parts forming the ball races will first be milled to practically a metaI-to-metal fit with the balls. Then the balls are installed and the coupling assembled. Thereupon the splines will be worked through their limits while applying the amount of torque anticipated for a normal operation. This construction and pre-operation produces a two-fold advantage: the ball races are work-hardened to an exact fit and a helix of the proper shape will be worn into the races, thereby reducing friction in operation and resulting in a longer life for the tool.

To further reduce friction in the coupling, the interior of thecoupling between the male and female members is sealed-off at points above and below the splines to form a chamber 11%. The seals comprise sealed piston 102 at one end, and at the other end a seal ring 109a which is seated in the exterior of coupling 114 to seal with the interior of section 118. Threaded openings 131, 131 provide communication with spaced points in chamber 1101) through the wall of female member 111 and are adapted to be closed by screw plugs 132. These openings are employed for introducing a suitable lubricant into chamber 11% to fill the latter so as to immerse the splines in the lubricant.

The present modification also includes a seal assembly 130 which is substantially identical with seal assembly 30 of the previously described embodiment and will not, therefore, be described in detail.

Operation of the coupling will be evident from the foregoing description of the device but it may be pointed out that as the coupling members are relatively extended and retracted, the anti-friction bearings between the spline elements will permit relatively frictionless movement under the various stresses to which the pipe string may be subjected. At the same time, the seal assembly will assure against leakage of fluid into and from the pipe string.

It will be understood that various changes and modifications may be made in the details of the illustrative embodiment but without departing from the spirit of this invention.

We claim:

1. An extensible coupling for well pipe strings, comprising:

(a) telescopically engaged inner and outer tubular members.

(b) means carried by the outer ends of the members for connecting them to adjacent sections of a pipe string,

(c) male and female spline elements cooperably disposed on the members to form a nonrotating longitudinally slidable connection between said members and to define a continuous bearing race therebetween,

(d) bearing means operably disposed in said bearing race, and

(e) male and female spline elements cooperably dismember and positioned in sealing relation between said coupling members below said connection, said sealing assembly comprising:

(i) inner, outer, and intermediate seal elements,

(ii) a first mounting ring pendently supporting said inner seal element,

(iii) a second mounting ring pendently supporting said outer seal element,

(iv) said intermediate seal element being mounted in a groove in the periphery of said second mounting ring,

(v) said outer seal element being constructed to define the relatively greatest effective sealing area about said inner coupling member, and

(vi) passageway means arranged to allow pressure fluid to act on the external surface of said outer seal element.

2. A coupling according to claim 1, wherein each of said seal elements is of a type actuatable in response to fluid pressure acting on its external surface to increase is sealing pressure about said inner coupling member.

3. A coupling according to claim 1, wherein said bearing means comprises a plurality of separate, unconnected cylindrical rollers having flat end surfaces and arranged in parallel to substantially fill said bearing race.

4. A coupling according to claim 1, wherein said bearing means comprises a plurality of balls filling said bearing race.

References Cited UNITED STATES PATENTS 1,686,945 10/1928 Abercrombie 285--302 X 2,764,428 9/1956 Murphy 285-302 X 2,979,147 4/1961 Naurnann 6423 X 2,991,635 7/1961 Warren 6423 X 3,225,566 12/1965 Leathers 321 X 3,319,726 5/1967 Brown 166.5 X

FOREIGN PATENTS 152,091 10/ 1920 Great Britain. 872,549 7/1961 Great Britain.

THOMAS P. CALLAGHAN, Primary Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 504,936 April 7, 1970 Cicero C. Brown et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 15, "male and female spline elements cooperably dis-" should read a sealing assembly carried by the outer tubular Signed and sealed this 22nd day of December 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents 

